Merge branch 'mab/gmsh_4.10_squashed'

Merge branch 'mab/gmsh_4.10_squashed'

Gmsh upgrade 4.8 -> 4.10.3

    - This commit adds interfaces MeshSizeFromCurvature which is used
    to control mesh size on curved edges (input [int] # of elements per
    2Pi).

    - Adds new algorithm for quad meshing from Gmsh based on frame-fields.

    - Corrects gmsh options for meshsizes.

    - Updates documentation.